This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 11-248299, filed Sep. 2, 1999, the entire contents of which are incorporated herein by reference.
The present invention relates to a plasma processing apparatus for applying a plasma processing such as an etching treatment and a film-forming treatment to a target object such as a semiconductor wafer.
In general, in the manufacture of a semiconductor device or an LCD device, a plasma processing such as a dry etching or a plasma CVD (Chemical Vapor Deposition) treatment is employed in many cases.
In an apparatus for performing plasma processing, a pair of electrodes are arranged to face each other within a chamber. A high frequency power is applied between these electrodes under a reduced pressure of a process gas atmosphere within the chamber. As a result, the process gas is converted into a plasma, and a plasma processing such as an etching or deposition is applied to the target object. The target object used in the plasma processing includes, for example, a semiconductor wafer and a glass substrate for an LCD device.
A chamber gate, which is an opening through which a semiconductor wafer is transferred into and out of the chamber, is formed in a side wall of the chamber of the plasma processing apparatus. The chamber gate includes an open portion (hole) made through the chamber wall and a gate valve for opening/closing the open portion. The semiconductor wafer is transferred into and out of the chamber by opening the gate valve, and the chamber is sealed by closing the gate valve when a plasma processing is applied to the target object.
Since a negative pressure is established within the chamber in general, the gate valve is arranged to close the open portion from the outside. Therefore, if viewed from the side of the inner wall of the chamber, a locally recessed space, hereinafter referred to as xe2x80x9cgate spacexe2x80x9d, is formed because the chamber wall has a certain thickness.
In the conventional plasma processing apparatus, the inner wall of the chamber has an opening (i.e., gate space). The gate surface is therefore exposed through the opening of the inner wall. Therefore, if a plasma processing for deposition is carried out, an undesired thin film is attached to the gate surface and the open portion of the gate space. During maintenance of the plasma processing apparatus, it is necessary to remove the undesired thin film which causes the particle generation. In the conventional plasma processing apparatus, it is necessary to manually wipe off the undesired thin film attached to the open portion by using, for example, a cloth impregnated with a solvent after the gate valve is opened. It is also necessary to wipe off the undesired thin film attached to the gate surface from inside the chamber, with the gate kept closed. Alternatively, it is necessary to wipe off the undesired thin film after the gate valve is detached. Such being the situation, it was highly laborious to remove the undesired thin film attached to the gate plane, etc. of the plasma processing apparatus.
What should also be noted, in addition to the undesired thin film formation caused by the depositing treatment, is that, if the open portion is exposed to the plasma, the surface region of the open portion is scattered by a sputtering effect. In the worst case, it is necessary to renew the chamber itself, leading to a shortened life of the plasma processing apparatus.
On the other hand, the inner wall surface of the chamber is designed to be free from projections and to form a flat surface even in the case of providing a shield. However, a recess for transferring a semiconductor wafer is required in the gate space, making it impossible to provide a shield. It follows that a projecting space is formed when viewed from the plasma space. Where a plasma processing is carried out with the projecting space left formed, the plasma runs about the projecting space so as to give rise to an abnormal discharge within the gate space. If an abnormal discharge takes place in the gate space, the etching rate of the semiconductor wafer is increased in the vicinity of the gate, with the result that the uniformity of the etching rate over the entire surface of the semiconductor wafer is impaired.
For overcoming the difficulties described above, it was customary in the prior art to bring about an abnormal discharge positively in the region other than the gate space so as to acquire balance with the abnormal discharge taking place in the gate space. However, a fundamental resolution has not yet been arrived at.
An object of the present invention is to provide a plasma processing apparatus that permits suppressing the abnormal discharge in the gate space so as to improve the maintenance capability of the chamber gate and prolong the life of the entire apparatus.
According to a first aspect of the present invention, there is provided a plasma processing apparatus for applying a plasma processing to a target object housed in a chamber, comprising a gate open portion formed in said chamber for transferring the target object into and out of the chamber, a gate valve for opening/closing the gate open portion, and a gate liner detachably mounted to cover the surface of the gate open portion and serving to prevent the gate open portion from being affected by the plasma during the plasma processing.
According to a second aspect of the present invention, there is provided a plasma processing apparatus, comprising a chamber whose inner space can be held in a vacuum state and in which a plasma processing is applied to a target object, an exhaust mechanism for exhausting the inner space of the chamber to establish a vacuum state, a gas introducing mechanism for introducing a process gas into the chamber, a lower electrode supporting the target object, an upper electrode arranged to face the lower electrode, a power source arranged outside the chamber for supplying an electric power to the electrodes so as to form a plasma of the process gas within the chamber, a gate open portion formed in the chamber for transferring the target object into and out of the chamber, and a gate valve for opening/closing the gate open portion, wherein a gate aspect ratio, which is a ratio of the depth of the opening of the chamber gate to the length in the short-side direction of the opening, is determined to prevent the abnormal discharge in the gate space in accordance with an anode/cathode ratio, which is a ratio of the area of the anode portion to the area of the cathode portion in the chamber.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.